According to a Take Two earnings call, Rockstar's got a top-secret project in the works due out for Xbox One and PS4 sometime this financial year - before March 2015, in other words.
We've rooted around in the Kotaku office rumour mill, and from what we can dredge up there's four things this secret project could be: that possible sequel to 2006's Bully we heard about a couple of years back (yay!); the fittingly secretive spy RPG Agent, which Rockstar claims is still in development, despite no-one having heard anything for ages (also yay); or a completely new IP (cautious, non-committal yay). Or, GTA V again, but on the next-gen consoles, which seems pretty likely. Slighty-more-muted-yay.
That's all we'll know until at least E3, when it's just possible that Take Two will give us something more. Or not, as Rockstar doesn't do E3. Be patient, basically.